Patent leather and coating composition for use in making same



Patented Jan. 19, 1954 assau t PATENT LEATHER AND COATING COMPO- SITION FOR USE IN MAKING SAME Salimuzzaman Siddiqui Dhar, Delhi, India, assignors to Council of Scientific and Industrial Research, New Delhi,

India l This inventionrelates to compositions particularly suited for the manufacture of patent leather and to the patent leather prepared by using them. H v

The term patent leather," also sometimes known as japanned leather or enamelled leather, as originally used applied to leathers finished essentially with linseed oil varnishes.

Usually, chrome-tanned'leather is employed for the purpose of making 'enamellecl leather. The

No Drawing. Application August 10, 1948, Serial No. 43,553v

2 Claims. (Cl. 117- 86) processes involved in the manufacture of these types of leather are very tedious and are zealously guarded as trade secrets. The number of varnish coats applied and their compositions differ from product to product and from factory to factory. Smooth japans often receive as many as six or seven coatings. Some tanners shorten the process by applying suitable lacquers over the first or daub coat or over the second coat. In any case the linseed oil varnishes in the final coatings are nowadays replaced to some extent by lacquers. Lately this practice has become so prevalent that in the so-calledffast coating finishes the finely ground pigmentary-dye lacquers do not contain any resins or gums. In almost all cellulose leather finishes resins andgums-are used only to a very limited extent. In certain cellulose leather finishes, resins such as dewaxed dammar or elemi or Albertol (trade name) with a trifle oi Venetian turpentine and acrylic resin are added in proportions up to 25% of the cellulose content,

but these do not appear to have met with particular success.

Among the chief difficulties encountered with lacquers for finishing leathers have been (a) lack of adhesion to the leather, with consequent peeling and (1)) absorption of the plasticisers by the leather, leaving thefilm very hard and incapable of contraction or expansion in use under changing conditions of atmospheric humidity and temperature. V

The object of the present invention is to overcome the above-mentioned drawbacks and to formulate a suitable and economical composition which can be made from easily available and, as far as possible, indigenous ingredients.

The present invention for the preparation of a ture of patent leather consists in preparing oil resin according to the process described in the specification of our Indian application, No. 38,06i, nowlndian patent, No. 38,064, and dissolving the said oil resin, along with film scraps, in butyl acetate and solvent naphtha. As described in said Indian patent the oil resin in question is composition particularly suited for the manufac- First formula: (first coating) I I Parts Butyl.acetate 35 Butanol or fusel oil 15 Methanol 15 Solvent naphtha 10 Turpentine j 10 Total p j Film scraps 6 011 resin 14 Dibutylphthalate ,4

W Second formula: (second coating) 1 1 p I Parts Butyl acetate 35 Butanol or fusel oil 15 Methanol 15 Turpentine 35 Solvent naphtha. 10

j Total f Film scraps 3 Oil'resin I 7 Bhilawan 'enamel y 5 Dibutyl phthalate 2 5 and Digish Chandra 2 prepared from bhilawan shell liquid by co-polymerizing the liquid with vegetable oils andwith an oleo-resinous material, selected from a class consisting of rosin and turpentine, by treatment with nitric acidwithin the temperature range of. from about 40 to 50 C. Bhilawan shell liquid can be obtained from bhilawan nuts as described in Indian Patent No. 32,237. As therein disclosed this liquid has been established as consisting mainly of a catechol derivative with a C15H21 side chain in the 3-position which has been named bhilawanol. Other components of bhilawan shell liquid are a small percentage of a monophenolic constituent named semi-carpol and a product of polymerization and condensation of bhilawanol. In respect of successive coatings, variations may be made in the ingredients as illustrated by the following formulae: i

The proportions of constituents are by weight. The proportionsgiven below are merely'illustrative and may be varied within a range of about 5 parts more orless, this applying, of cours e,'only to the major components of the compositions.

Castor oil -r i'n th'e... lacquers made hitherto.

Third formula: (third coating) Parts Butyl acetate 27 Butanol orfusel oil- -u -l 23 Methanol; l 15 Solvent naphtha 10 Acetone I:

Total 85 Film scraps -I 4 Dibutyl phthalate 2 It is a well-known fact that large quantities of cinematographic films, which are definitely cheaper than the usual graded; solution of. cellulose nitrate or cellulose esters, are available at nominal prices. Hence these films are preferably made use of in the present invention.

, Lacquer without resin'has hitherto been a costly' composition. important feature of the present invention is the; use of acomparatively larger quantity" of resin which besides bringing down the price of. the ultimate product, imparts flexibility to the leather and fulfils the important requirement of anchorage or adhesion and also gives.- body to. the lacquer.

Lacquers in the trade. for application to leather contain higher proportions of active organic solvents and little or no resin. whereas in the: first formula above it will be noticed that a highly Concentrated, Solution has been evolved with considerable. saving. in solvents. All the solvents used in thi'sfprocess are readily available at commercial prices. Oil of turpentine was first used by Field in 1890, but it isnota common ingredient Its presence in this composition has been. foundv to increase the flow of. the lacquer and. also to improve the. gloss ofthefil'm.

The difliculty of. proeuringgfinely ground pigments suitable for. use. in these finishes'has been lawan resin itself is obtained byheating bhilawan shell liquid in' the presence of metals, selected from a class consisting of zinc, tin, lead and their. alloys, as" describedin the Journal of Scientific and Industrial Research, vol. 1, No. 1, page 20,

column 2, and in Indian patents, Nos; 28,0D21 to 28,005 29,051 and.29,93.8.. It-iisthe'reshowrr that bhilawan. resin. is. insoluble in. alcohol but. soluble in turpentine andhydrocarbons.

The. leather finishes in vogue are essentially highly plasticised. On account of the high inherent flexibility of the oil resin in thencomposi- I tions described in the present application, only a comparatively small quantity of plasticiser. has to be used. Dibutyl phthalate and commercial castor oil have been chosen in consideration of their lower prices.

The essential details that have to lie-observed. in the preparation "of lacquers forfi'rst, second" and third coatings are as follows:

This

mesh).

'4 The removal of the silver salts from the cinematographic films by means of a solution of quicklime and caustic soda. forms the preliminary operation.

First formula (for first coating) Second formula (for second coating) The oil. resin ('7 parts), film scraps (3 parts) andbhilawan enamel (5 parts), butyl acetate (35 parts)- and solvent naphtha (10 parts) are kept in agitation in a shaking machine for 3- to 4 hours., When. the resin, film scraps and enamel are: well dispersed, the solution is diluted with a mixture of methanol. (.15 parts), butanol or f'usel oil (L5parts)- and. turpentine (35 parts). The resulting; solution is filtered through a 200 mesh sieve. Finally dibutylphthalate (2 parts) and castor oil (5- parts) are added and well mixed.

Third formula-(for third coating Film scraps (4 parts) are; dissolved in a mixture of butylacetate (27 parts), butanol or fusel oil Ztlpartsl, methanol: (15' parts), solvent naphtha (I0 parts) and acetone (10 parts). In order: to dissolve the films quickly the solution is kept in agitation a shaking machine for 3' to 1' hours. solution is filtered through a. sleeve (200 Finally dibutyl phthalate (2 parts.) is added. 7

The-coating compositions prepared as described above maybe applied to leather (preferabl, chrome-tanned) in the manner widely known in the patent leather trade;

I claim; V

i. A coating composition particularly adapted for use in producing a base coat in the manufacture of patent leather which comprises butyl acetate 35 parts, "a solvent selected from a class consisting of butanol and fus'el oil 1 5 parts, methanol 15 parts, solvent nap'l-itliaa 10 parts, turpentine lof-parts, fi l'ur scrap- 6 parts; oil resin 1A parts and d'ibutyl phthalate; the major components of said composition being maintained within the range of from about 5' parts above to 5 parts" below the specific proportions indicated the said oil 'resinbeing the" product resulting from the copolymerization of bhilawan shell liquid with a vegetable oil and with an ol'eore'si'nous materia'f, selecmd from-a class consisting of resin and turpentine, by treatment with nitric acid at' a temperature of from about 40" to 50 C. v

2. A patent? leather" comprising a base of chrome-tanned leather coated with a composite coating comprising the" dried and'hardened resiclues of the following three coating compositions applied in the sequence indicated: 7 a first composition comprising butyl acetate 35 parts, a solvent selected from a class consisting of butanol and fusel oil 15' parts; methanol 15 parts, solvent naphtha 1"0 partsyturpenti'ne 10 parts, filhr scrap 6- parts, oil resin 14 parts and d'ib'utyl phthalate 4 parts; a second composition comprising butyl acetate 35 parts, a solvent selected from a class consisting of butanol and fusel oil 15 parts, methanol 15 parts, solvent naphtha parts, film scrap 3 parts, oil resin '7 parts, Bhilawan enamel 5 parts, dibutyl phthalate 2 parts, castor oil 5 parts; and a third composition comprising butyl acetate 27 parts, a solvent selected from a class consisting of butanol and fusel oil 23 parts, methanol parts, solvent naphtha 10 parts, acetone 10 parts, film scrap 4 parts and dibutyl phthalate 2 parts; the major components of the three compositions being maintained within the range of from about 5 parts above to 5 parts below the specific proportions set out the said oil resin being the product resulting from the copolymerizationof bhilawan shell liquid with a vegetable oil and with an oleoresinousmaterial, selected from a class consisting of rosin and turpentine, by treatment with nitric acid at a temperature of from about to C.

SALIMUZZAMAN SIDDIQUI. DIGISH CHANDRA DHAR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Grifiiths Dec. 29, 1931 Hall July '7, 1986 Shankweiler Mar. 15, 1938 Moss July 12, 1938 Booty et al Jan. 10 1939 Nebel Aug. 1, 1939 Russell Nov. 28, 1939 Thinius Nov. 18, 1941 Scripture Dec. 29, 1942 FOREIGN PATENTS Country Date Great Britain 1871 

1. A COATING COMPOSITION PARTICULARLY ADAPTED FOR USE IN PRODUCING A BASE COAT IN THE MANUFACTURE OF PATENT LEATHER WHICH COMPRISES BUTYL ACETATE 35 PARTS, A SOLVENT SELECTED FROM A CLASS CONSISTING OF BUTANOL AND FUSEL OIL 15 PARTS, METHANOL 15 PARTS, SOLVENT NAPHTHA 10 PARTS, TURPENTINE 10 PARTS, FILM SCRAP 6 PARTS, OIL RESIN 14 PARTS AND DIBUTYL PHTHALATE; THE MAJOR COMPONENTS OF SAID COMPOSITION BEING MAINTAINED WITHIN THE RANGE OF FROM ABOUT 5 PARTS ABOVE TO 5 PARTS BELOW THE SPECIFIC PROPORTIONS INDICATED THE SAID OIL RESIN BEING THE PRODUCT RESULTING FROM THE COPOLYMERIZATING OF BHILAWAN SHELL LIQUID WITH A VEGATABLE OIL AND WITH AN OLEORESINOUS MATERIAL, SELECTED FROM A CLASS CONSISTING OF ROSIN AND TURPENTINE, BY TREATMENT WITH NITRIC ACID AT A TEMPERATURE OF FROM ABOUT 40* TO 50* C. 